Muzzle end mounted firearm accessories are available for attachment to the barrel of firearms to accomplish various effects when the firearm is operated. Silencers are an example of such an accessory and include baffled chambers to slow the release of pressure from the barrel of the firearm. The slowed release of pressure reduces the audible report during firing. Flash hiders are another type of muzzle end accessory that include features to mix unburnt gunpowder and air in a manner that reduces the overall brightness of a flash that may occur during firing. Generally speaking, silencers and flash hiders may be mounted to the muzzle end of a firearm barrel in different rotational orientations without affecting the operation of the accessory.
Some muzzle end mounted accessories are designed for mounting to a firearm barrel in one or more particular rotational orientations to accomplish a desired effect. Muzzle brakes redirect a portion of combustion gases sideways or rearward, with respect to the firing direction, as the gases escape from a barrel when a shot is fired. As the gases are redirected, the firearm is pushed forward in a manner that counteracts recoil of the firearm. Muzzle brakes are typically mounted to a firearm barrel in a particular rotational orientation, such as to prevent gases from being redirected upward into the line of sight of the firearm operator. The manner of rotationally orienting a muzzle end accessory on the barrel is often referred to as timing the accessory to the barrel.
Compensators are another type of muzzle end accessory that is timed to one or more particular rotational orientations when mounted to a firearm barrel. Compensators redirect the flow of gasses that escape from a barrel during firing in an overall upward direction. The resulting force that acts against the firearm counteracts other forces that urge the muzzle end of a rifle upward during firing.